Direct positive photographic silver halide emulsions and elements containing water insoluble polymers



United States Patent Int. Cl. G03c 1/04 US. Cl. 96-114 16 Claims ABSTRACT OF THE DISCLOSURE Fogged direct-positive photographic silver halide emulsions having a binding agent comprising a hydrophilic colloid and an aqueous dispersion of a water-insoluble polymerized vinyl compound exhibit improved photographic properties. Elements comprising said emulsions are disclosed.

This invention relates to photographic materials, their preparation and use. In one of its aspects, this invention relates to improved photographic silver halide solarizing emulsion layers and photographic elements containing these layers. In a specific aspect, this invention relates to fogged, direct-positive photographi silver halide emulsion layers having a binding agent comprising a hydrophilic colloid and a water-insoluble polymerized vinyl compound.

The use of fogged, direct-positive photographic silver halide emulsions in the photographic field to obtain positive images is well known. However, when photographic elements containing fogged, direct-positive photographic silver halide emulsion layers are physically deformed during handling, for example, by bending, fog or latent image is removed from the silver halide in the grains present in the physically deformed areas, causing a loss in D,,,.,,,; upon development. This results in the formation of white spots in the affected areas in the processed materials. This is obviously undesirable, particularly in graphic arts applications where such materials must meet very high standards.

Accordingly, it is an object of this invention to provide a means for reducing the loss in maximum density exhibited by fogged, direct-positive photographic silver halide emulsion layers upon physical deformation.

It is another object of this invention to provide photographic silver halide emulsions and elements exhibiting improved photographic properties.

It is another object of this invention to provide a fogged, direct-positive photographic silver halide emulsion having a binding agent comprising a hydrophilic colloid and an aqueous dispersion of a polymerized vinyl compound.

Still another object of this invention is to provide a photographic element bearing a layer of a fogged, direct-positive photographic silver halide emulsion having a binding agent comprising a hydrophilic colloid and a water-inso uble polymerized vinyl compound.

Other objects of this invention will become apparent from an examination of the specification and claims that follow.

In accordance with this invention, it has been found that the above and other objects can be attained with a fogged, photographic silver halide solarizing emulsion wherein the binding agent comprises a hydrophilic colloid and an aqueous dispersion of polymerized vinyl compound.

One embodiment of this invention relates to a fogged, direct-positive photographic silver halide emulsion in which the binding agent comprises a hydrophilic colloid "ice and an aqueous dispersion of polymerized vinyl com pound.

Another embodiment of this invention relates to a photographic element comprising a support and at least one fogged, direct-positive photographic silver halide emulsion layer in which the binding agent comprises a hydrophilic colloid and water-insoluble polymerized vinyl compound.

In US. Pat. 3,142,568 issued July 28, 1964, it is shown that a number of properties, including dot quality, contrast and dimensional stability of a photographic silver halide layer can be improved if the binding agent employed in the layer comprises a mixture of gelatin and a polymerized vinyl compound, and the layer contains an amphoteric dispersing agent and a polyethylene glycol or ether thereof. However, it could not have been expected that the use of a binding agent comprising a hydrophilic colloid and a water-insoluble polymerized vinyl compound in fogged, direct-positive photographic silver halide emulsion layers would increase the resistance of such layers to loss in D,,,,,, upon physical deformation. Furthermore, as shown in the following Example 6, the use of water-soluble vinyl polymers such as polyacrylamide, rather than the water-insoluble polymerized vinyl compounds disclosed herein, does not give the desired protection against loss in maximum density obtained in the practice of this invention.

One component of the binding agent for the photographic silver halide emulsions described herein is an aqueous dispersion of polymeric vinyl compound. The preferred polymeric vinyl compounds are homo or copolymers prepared from acrylic acid and esters thereof. These polymers are insoluble in water and can be readily dispersed in water and mixed with a suitable hydrophilic colloid such as gelatin. The vinyl polymers are generally employed in concentrations in the range of about 20 to about most often concentrations at least 50%, by weight, based on the combined weight of hydrophilic colloid and polymerized vinyl compound. The remainder of the binding agent is a hydrophilic colloid such as gelatin, alone or with another photographic binding mat rial. Good results are achieved with polymers of alkyl acrylates or methacrylates which are obtained by homopolymerizing these monomers or interpolymerizing these monomers with each other or with different ethylenically unsaturated polymerizable compounds, containing one or more groups, or more particularly, one or more CH2=C groups, to form water-insoluble addition polymers. In general, it is desirable to employ a polymeric vinyl compound which contains, in polymerized form, at least 65%, preferably about 75 to about by weight, of an alkyl acrylate or methacrylate, as exemplified by ethyl acrylate, methyl acrylate, butyl acrylate, ethyl methacrylate, octyl 'methacrylate, and the like. Suitable ethylenically unsaturated comonomers which can be interpolymer ized with these materials to form water-insoluble addi 1 tion polymers include, for exampl vinyl esters, amides. nitriles, ketones, halides, ethers, e o-unsaturated acids or esters thereof, olefins, diolefins and the like, as exemplified by acrylonitrile, methacrylonitrile, styrene, tat-methylstyrene, vinyl chloride, vinylidene chloride, methyl vinyl ketone, vinyl acetate, fumaric, maleic and itaconic acid esters, 2 chloroethylvinylether, methylenemaleonitrile, acrylic acid, methacrylic acid, dimethylaminoethylmethacrylate, N-vinylsuccinimide, N-vinylphthalimide, N- vinylpyrrolidone, butadiene, isoprene, vinylidene cyanide and the like. The polymeric vinyl compounds most useful in the practice of this invention generally have an average molecular weight in the range of about 5000 to about 500,000 and a particle size in the dispersion which is generally less than about 1 micron, often less than about 100 m Many polymers of this type are disclosed in U.S. Pat. 3,142,568, issued July 28, 1964.

A preferred class of vinyl polymers which can be employed in the practice of this invention are Water-insoluble interpolymers of acrylates or methacrylates with acrylic acid and a sulfobetaine having the formula:

where R, R and R are each hydrogen or alkyl and R and R are each divalent saturated hydrocarbon radicals, desirably containing up to 12 carbon atoms. Suitable sulfofetaine monomers include, for example, 5,5,l-trimethyl 9 oxo 8 oxa 5 azonia-lO-undecene-l-sulfonate, 4 t butyl 9 methyl 8 oxo 7 oxa-4-aza-9-decenel-sulfonic acid, 4,4,9 trimethyl 8-oxo-7-oxa-4-azonia-9- decene-l-sulfonate, and the like. The preferred polymers of this type contain, in polymerized form, at least 75%, preferably about 75 to about 93%, by weight, of acrylate or methacrylate, up to about preferably about 5 to about 15%, by weight, acrylic acid and up to about 10%, preferably about 2 to about 10%, by weight, of the sulfobetaine.

A very convenient method for preparing the sulfobetaine monomers used in preparing the aforementioned preferred class of polymeric vinyl compounds comprises reacting the appropriate amino alkyl ester of an unsaturated carboxylic acid with the appropriate sultone. Such, a

reaction can be carried out in the presence of an organic solvent such as acetonitrile, a liquid hydrocarbon or a ketone such as acetone at temperatures up to about 100" C., preferably 50 to about 80 C. In general, the reaction is complete in less than 8 hours, often in about 2 to about 6 hours. The reaction is not pressure dependent and therefore superatmospheric or subatmospheric pressures can be employed. The resulting sulfobetaine can be isolated by conventional procedures. The reactants are generally employed in stoichiometric concentrations although slight excesses of either reactant can be employed. As is obvious to one skilled in the art the specific reaction conditions, for example, temperature, pressure, and the like, will depend upon the particular amino alkyl ester and sultone employed. Another suitable method for. preparing the sulfobetaines, particularly .where R and R in the above formula, are both hydrogen, .is to react the appropriate hydroxyalkyl amine with the required sultone and then esterify with acrylic acid or with a derivative thereof.

Another class of polymeric vinyl compounds which is preferred in the practice of this invention is the interpolymers of; alkyl acrylates or methacrylates with sulfoesters having the formula: V

alkyl radicals containing up to about l2 carbon atoms,

often 1-8 carbon atoms, as exemplified by methyl, ethyl, propyl, pentyl, octyl, dodecyl and the like. R 'has its can be any aliphatic, cycloaliphatic or aromatic radical and will generally contain up .to about 12.carbon atoms.

Preferred hydrocarbon R radicals are alkylene radicals, generally those containing 2-4 carbons. R can also be a divalent aliphatic hydrocarbon radical in which there is a O- and/or -S- radical and generally contains up to 12 carbon atoms. Such R radicals can, therefore, be saturated or unsaturated, althoughsaturated.

divalent alkylene groups in which the carbon chain is interrupted by oxygen and sulfur atoms are preferred.

Suitable R radicals include, for example, ethylene 1,3- propylene, 1,2-propylene, tetramethylene,

1,3-isobutylene, pentamethylene, hexamethylene, octamethylene, phen ylene, bisphenylylene, naphthylene, cyclopentylene, cyclo hexylene, Z-butenylene, butynylene, 2-oxatrimethylene, 3""

thiapentamethylene, and the like. M is a cation, as exemplified by hydrogen, an alkali metal such as sodium or potassium, ammonium, the cation of an organic'arnine such as 'triethyl amine, diethanol amine and the like.

The sulfoesters can be preparedusing any method knownto be-suitable for thlSPUIPOSESpFOI example, U.S. Pat. 2,923,734, issued Feb. 2, 1960, discloses the preparation of such esters by the reaction of an a-methylene carboxylic acid with an aliphatic hydroxy sulfonic acid while U.S. Pat. 3,024,221, issued Mar. 6,- 1962, discloses a method forv preparing the sulfoester by reacting the appropriate acyl halide With the salt of the hydroxy sulfonic .lacid. Examples of hydroxy 'sulfonic acids (and their salts) that canbe employed to form the sulfoesters are 2-hydroxyethane sulfonic acid, Z-hydroxy-l-propane sulfonic acid, l-hydroxy '2 butane sulfonic acid, 2-hydroxycyclohexane sulfonic acid, p-phenolsulfonicacid,

2-(2 hydroxyethoxy)ethane 1 sulfonic acid, 2-(2- hydroxyethylthio-)ethane 1 sulfonic acid, 4-hydroxy-2- butene-l-sulfonic acid, 4-hydroxy 2 butyne-l-sulfonie acid and the like. u-Methylene carboxylic acids or acyl halides include acrylic acid, methacrylic acid, tit-butylacrylic acid, acyloyl chloride, methacryloyl bromide, ochexylacryloyl chloride and the like. The preferred class of polymers of the sulfoesters generally contains, in"

polymeric form, at least 65%,prefera'bly about to about by Weight, of the alkyl acrylate' or meth-- acrylate and up to about 15%, preferably about 5 to I about 15%,by weight, of the sulfoester.

The temperature at -which the polymeric vinyl prepared is subject to-Wide variation since this temperacom pounds employed in the practice of this'invention are ture depends upon such variable: features as'the specific monomer used, duration of heating; pressureemployed andlike considerations. However; the polymerization" temperaturegenerall'y does not exceed about- C., r

and most often, is inthe range 'of about-50 to about 90- C. Thepoly'merization can be carried outin suitable" solvents or diluents, for example, wate'r or'frnixturesof water with' water miscible solvents, as-exemplifie'd by" methanol, "ethanol," propanol, -isopr'opyl* alcohol, "fbutyl 1 alcohol, and the like. The pressure employed in the polymerization, "if any, usually only sufiicieutto'rnain'. tain the reaetiQn'miXture in liquid form, altl 1ough' either I' superatmospheric or subatjru sphr c,pressures canfbe used. The concentration of polymeri zlablemonorner in the polymerizationmixture canrbe varied widelyl with n n rat ons PL-IQL Q t-. ln ee y we ht, and..

P efe ab y bou 2 w about per nt. by w tcbased;

on the :weight- -of the vehicle beingsatisfactory. suita'ble;

catalysts forthepolymerization :reactiondnclude, for

example, the free radical catalysts, such as hydrogen peroxide, cumene hydroperoxide, water soluble azo type initiators and the like. In redox polymerization systems the usual ingredients can be employed. If desired, the polymer can be isolated from the reaction vehicle by freezing, salting out, coagulation or by using other separation procedures suitable for this purpose.

The photographic silver halide can be dispersed in the binding agent in a variety of ways, for example, an aqueous dispersion of the photographic silver halide in hydrophilic colloid, preferably gelatin, can be mixed with an aqueous dispersion of the polymeric vinyl compound. Alternatively, the photographic silver halide can be precipitated in an aqueous dispersion of the polymeric vinyl compound and hydrophilic colloid. In this case, a Water soluble silver salt such as silver nitrate is admixed with the silver halide such as potassium bromide in the presence of the mixture. In still another procedure, the photographic silver halide is precipitated in hydrophilic colloid, e.g., an aqueous gelatin solution, and digested in the conventional manner known to the art. After digestion, but prior to coating, there is added to the emulsion an aqueous dispersion of the polymeric vinyl compound. The bulk of the resulting dispersion can be increased by the addition of more of the polymeric vinyl compound and/or natural or synthetic colloid or other binding material suitable for use in photographic silver halide emulsions. l

The hydrophilic colloid which constitutes one com ponent of the binding agent for the photographic silver halide emulsion described herein is preferably gelatin. However, other hydrophilic colloids can be employed in place of or in combination with gelatin. Thus, the binding agent can also comprise other binding materials such as natural and/ or synthetic water soluble polymers, particularly water soluble vinyl polymers, as exemplified by mono and polysaccharides, cellulose derivatives, proteins, water soluble polyacrylamides, polyvinyl pyrrolidones, and the like. In the preferred case, the bind ing agent comprises a mixture of polymeric vinyl compound, in a concentration in the range of about 20 to about 80 percent, by weight, with the remainder of the binding agent being gelatin. Typical hydrophilic colloids that can be used in the binding agent include for example, gelatin, colloidal albumin, cellulose derivatives, synthetic resins, for example, polyvinyl alcohol, acrylamide polymers, and the like.

Any of the photographic silver halides can be used in the preparation of the fogged, direct-positive photographic silver halide emulsions employed in the practice of this invention as exemplified by silver bromide, silver chlorobromoiodide, silver chlorobromide, silver chloride and the like. The photographic silver halide emulsions can be lithographic silver halide emulsions in which the halides generally comprise a mixture of chloride and bromide. Such high contrast emulsions preferably contain less than mole percent iodide. These photographic silver halide emulsions can contain silver halide grains which form latent images predominantly on the surface of the grains or those which form latent images predominantly inside the silver halide crystals, as exemplified by those described in Davey and Knott U.S. Pat. 2,592,250, issued Apr. 8, 1852, Luckey and Hoppe U.S. Pat. 2,996,302, issued Aug. 15, 1961, and Luckey and Hoppe U.S. Pat. 3,178,282, issued Apr. 13, 1965. The preferred photographic emulsions are those which have high internal sensitivity and low surface sensitivity.

The fogging ofthe photographic emulsions used in the, practice of this invention can be effected using any method suitable for this purpose. For example, such fogging can be accomplished by exposing the emulsion to light as described in Shirk U.S. Pat. 2,944,897, issued July 12, 1960. Other methods such as chemical fogging methods can also be used. For example, fogging can be effected by chemical sensitization to fog using chemical sensitizing agents such as gold or noble metal sensitizers, sulfur sensitizers such as labile sulfur compounds and the like. The emulsions can also be fogged by treating with reducing agents such as formaldehyde, stannous chloride, thiourea dioxide and the like as described, for example, in Hillson U.S. Pat. 3,062,651, issued Nov. 6, 1962. The fogging is generally sufficient to give a density of at least 2.0 when the coated emulsion is processed in a photographic developer.

The photographic compositions described herein can be coated on a wide variety of supports. Typical supports are the flexible supports of materials such as metal, paper, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyolefin film, polycarbonate film, polyethylene terephthalate or other polyester film and other related materials. Supports such as paper which are partially acetylated or coated with an a-olefin polymer, particularly a polymer of an oc-Olefin containing 2-10 carbon atoms, as exemplified by polyethylene, polypropylene, ethylene butene copolymers and the like, give good results.

Photographic silver halide emulsion layers and other layers present in the photographic elements made according to the invention can be hardened with any suitable hardeners such as aldheyde hardeners, aziridine hardeners, hardeners which are derivatives of dioxane, oxy polysaccharides, such as oxy starch, oxy plant gums and the like. The photographic emulsions can also contain additional additives, particularly those known to be beneficial in photographic emulsions, including for example, stabilizers, particularly the water soluble inorganic acid salts of cadmium, cobalt, manganese and zinc such as disclosed in U.S. Pat. 2,829,404, the substituted triazaindolizines as disclosed in U.S. Pat. 2,444,605 and 2,444,- 607, spectral sensitizers such as the cyanines, merocyanines, complex (trinuciear) cyanines, complex (trinuclear)merocyanines, styryls, hemicyanines, speed increasing materials, plasticizers, absorbing dyes, and the like. If desired, coating aids can also be used in the photographic emulsions. Typical coating aids are the anionic, nonionic and amphoteric surface active compounds.

It may also be desirable to add certain onium salts such as quaternary ammonium salts, sulfonium salts and phosphonium salts to the light-sensitive emulsions disclosed herein to increase development rate. Examples of the quaternary ammonium salts include nonyl pyridinium perchlorate, hexoxymethyl pyridinium perchlorate, ethylene bis-dioxymethyl pyridinium perchlorate and others described by Carroll U.S. 2,271,623, issued Feb. 3, 1942, hexadecamethylene-l,l6-bis(pyridinium perchlorate), 9 16 diaza-7,18-dioxa-8,17-dioxotetracosane-,

l,24-bis(pyridinium perchlorate), and others of Beavers et al., U.S. 2,944,898, issued July 12, 1960. Other examples include the onium salts of polyoxyalkylenes of Carroll et a1. U.S. 2,944,902, issued July 12, 1960, the poly-' onium salts of Carroll et a1. U.S. 2,288,226, issued June 30, 1942, such as bis(lauryl methyl sulfonium p-toluene sulfonate) 1,2-ethane, N,N'-trimethylene dioxymethyl pyridinium perchlorate, etc., the sulfonium salts of Carpressing a sample of film containing such a layer between two plates, one of which has a raised triangle and the other of which has a triangle of about three times the area of the first cut in it. The raised triangle is an isosceles triangle, the longer sides being about inch in length, the shorter side being about 7 inch in length. The offset of the raised triangle is about A inch and the proportions of the depressed triangle are the same as those of the raised triangle. For testing purposes, a three kilogram weight is applied to the top of the raised triangle. The loss in D after development of the coating, fixing and washing in the usual manner can be rated on the basis of for no loss in maximum density, 1 for very slight loss, 2 for slight loss, 3 for moderate loss and 4 for severe loss. These results are determined by comparison between the density of the unaffected and deformed portions of the film or by making actual density measurements with suitable equipment.

This invention can be further illustrated by the following examples of preferred embodiments thereof although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAMPLE 1 When a binding agent comprising a hydrophilic colloid and a polymerized vinyl compound is employed in a fogged, direct-positive photographic silver halide layer there is a reduction in D loss upon deformation. Furthermore, polymerized vinyl compounds prepared from alkyl acrylates and sulfobetaine monomers are particularly eifective in practicing this invention. To illustrate, a latex of copoly(n-buty1 acrylate-acrylic acid-4,4,9 trimethyl-8-oxo-7-oxa-4-azonia-9-decene-l-sulfonate) is prepared in the following manner: A solution of 12.2 g. (0.10 mole) of 1,3-propane sultone and 15.7 g. (0.1 mole) of dimethylaminoethyl methacrylate and 100 ml. of acetonitrile is refluxed for 2 hours. The precipitated product is separated from'the liquid, washed with hot acetonitrile and dried in vacuum. There are obtained 27.4 g. of white crystalline 4,4,9 trimethyl 8 oxo-7-oxa-4- azonia-9-decene-l-sulfonate.

The sulfobetaine monomer is copolymerized with alkyl acrylate and acrylic acid to form the polymerized vinyl compound using the following procedure: 375 ml. of distilled water is placed in a flask, heated to 80 C. and degassed with nitrogen. Then 3.9 ml. of Triton 770 (40% solution), 1.5 g. of potassium persulfate and 0.5 g. of sodium bisulfite are added in the order given. After the additions, the following two solutions are added under nitrogen with vigorous stirring over 12 minutes: 1) a solution of 138.6 g. of n-butyl acrylate and 15.4 g. of acrylic acid and (2) 3.9 m1. of Triton 770 (40% solution) and 12.5 g. of 4,4,9-trimethyl-8-oxo-7-aza-4-azonia- 9-decene-1-sulfonate, prepared as above in 125 ml. of water. After the liquid mixture is stirred for an additional 30 minutes at 80 C. it is diluted to 10% solids with water.

The polymer obtained using the above procedure is employed in practicing this invention as follows: A fine grain silver chlorobromide emulsion having grains with a surface of silver bromide, as described in MacWilliams US. Pat. 2,756,148, issued July 24, 1956, is fogged using thiourea dioxide according to the procedure described in Hillson US. Pat. 3,062,651, issued Nov. 6, 1962. The emulsion is coated on conventional cellulose acetate film base at a coverage of 308 mg. of silver per square foot and 306 mg. of gelatin per square foot without copolymer (Coating A-Control), With 39.4 g. of copolymer per mole of silver halide (Coating B) and with 65.6 g. of copolymer per mole of silver halide (Coating C). The coatings are subjected to the deformation test described hereinabove, exposed in an Eastman IB sensitometer, developed for 2% minutes in Kodak Developer D-85, fixed, washed {Triton 770 is a surfactant composition composed of a sodium alkyl aryl polyether sulfate and isopropanol, manufactured by Rohm and Haas C0.

and dried in the conventional manner. The loss in D determined as described hereinabove, is as follows:

TAB LE 1 Copolymer (g./m0le Coating AgX) D Loss A (control) 4 B 39. 4 1 C 65. 6 0

Similar results are obtained when the above procedure is repeated with copolymers in which the sulfobetaine monomer described above, in combined form, is replaced by other sulfobetaine monomers, in combined form, such as In each case the loss in D is 2 or less.

EXAMPLE 2 A latex of copoly(methyl acrylate-sodium 4-acryloyloxybutane-Z-sulfonate) (:5 Weight percent) is prepared in the following manner: 375 ml. of distilled water is placed in a flask, heated to 95 C. and purged of oxygen by bubbling in nitrogen. To the water is added 4 ml. of Triton 770 (40% solution), 1.0 g. of potassium persulfate and 0.1 g. of sodium bisulfite. The following monomer and solution are then added simultaneously under nitrogen with vigorous stirring over a period of 15 minutes: (1) 118.7 g. of methylacrylate and (2) a solution of 6.3 g. of sodium 4-acryloyloxybutane-2-sulfonate, 0.23 g. of sodium bisulfite and 4 ml. of Triton 770 in ml. of distilled water. After the polymerization mixture is stirred for an additional 30 minutes at 95 C. the resulting latex is chilled and raised to pH 5.0 with an aqueous sodium hydroxide solution.

The copolymer prepared using the above procedure is incorporated into the fogged, direct-positive photographic silver halide emulsion layer of Example 1 using the procedure described in that example. Coating A is the control and contains no copolymer while Coating B contains 59.5 grams per mole of silver halide of copolymer. After deformation, exposure, development and processing as in Example 1, the results are as follows:

EXAMPLE 3 As already indicated, the concentration of polymerized vinyl polymer in the binding agent is subject to variation. To illustrate, copoly(methyl acrylate-sodium-4-acryloyloxypropane-Z-sulfonate) (95.5 weight percent) is prepared using the polymerization procedure of Example 2 with sodium-4-acryloyloxypropane-2-sulfonate. 59.5 g. of the copolymer per mole of silver halide is incorporated into the fogged, direct-positive photographic silver halide emulsion of Example 1 which is coated using the procedure in Example 1, except that the gelatin coverage is reduced to mg. of gelatin per square foot. Coating A contains no additional copolymer and Coating B contains 59.5 g. of copolymer per mole of silver halide. lAfter deformation, exposure, development and processing as in Ex'ample 1 the following results are obtained:

TABLE 3 Copolymer (g./mole Coating AgX) maz.10SS

A (control) 4 B 59. 2

EXAMPLE 4 TABLE 4 Copolymer (gJmole Coating AgX) m n. loss A (control) 4 B 59. 5 1

Similar results are obtained when copoly(ethyl methacrylate acrylic acid), copoly(ethyl acrylate itaconic acid), copoly(ethyl acrylate acrylic acid), as described in US. Pat. 2,754,280, are employed in the above procedure.

EXAMPLE 5 As already indicated, the binding material employed in the practice of this invention can contain other hydrophilic colloids, particularly water soluble polymers such as polyacrylamides, in combination with gelatin. To illustrate, the procedure of Example 1 is repeated using'a binding material comprising a water soluble polyacrylamide prepared according to the procedure of Minsk et al. UN.S. Pat. 2,486,191, issued Oct. 25, 1949, gelatin and copoly(methyl acrylate-sodium-4-acryloyloxypropane- 2-sulfonate) of Example 3 (Coating B) or copoly(n-butyl acrylate acrylic acid) of Example 4 (Coating C). The emulsion is coated on conventional polyester film base at a coverage of 412 mg. of silver per square foot. After exposure, development and processing as in Example 1 the loss in D upon deformation is as follows:

TABLE 5 Gelatin Copolymer Polyacryl- (g./mo1e (g./mo1e amide (g./

AgX) AgX) mole AgX) Dmnx. loss In addition to reducing loss in D in the areas affected by physical deformation, it has also been found that the use of the binding agents containing both water soluble polymers and gelatin with the water insoluble vinyl polymers actually increases Dmax, in the unaffected areas.

EXAMPLE 6 As already indicated, water-soluble polymerized vinyl compounds such as polyacrylamide are not effective to reduce loss in D when employed as one component of the binding agent according to the practice of this invention. To illustrate, 65.6 g. and 96.0 g. of water-soluble polyacrylamide prepared according to the procedure described in Minsk et al. US. Pat. 2,486,191, issued Oct. 25, 1949, are incorporated into separate coatings of the fogged, direct-positive photographic silver halide emulsion layer of Example 1 using the procedure described in that example. |After deformation, exposure, development and processing as in Example 1 each coating exhibits a D loss of 4, indicative of a severe loss in D Thus, by the practice of this invention there is provided a means for reducing the loss in D exhibited by fogged, direct-positive photographic silver halide emulsion layers upon physical deformation.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A fogged, direct-positive, photographic silver halide emulsion in which the binding agent comprises a hydrophilic colloid and an aqueous dispersion of waterinsolu-ble polymerized vinyl compound, said water-insoluble polymerized vinyl compound being present in the binding agent in an amount from about 20 to about by weight, based on the combined weight of the said hydrophilic colloid and said water-insoluble polymerized vinyl compound.

2. The photographic silver halide emulsion of claim 1 in which the hydrophilic colloid is gelatin.

3. The photographic silver halide emulsion of claim 1 in which the water-insoluble polymerized vinyl compound is an alkyl acrylate polymer.

4. The photographic silver halide emulsion'of claim 1 in which the hydrophilic colloid is gelatin and the water-insoluble polymeric vinyl compound is an alkyl acrylate polymer.

5. A fogged, direct-positive, photographic silver halide emulsion having high internal sensitivity and low surface sensitivity in which the binding agent comprises gelatin and an aqueous dispersion of water-insoluble alkyl acrylate polymer, said binding agent comprising about 20 to about 80%, by weight, of said alkyl acrylate polymer, based on the combined weight of gelatin and alkyl acrylate polymer.

6. The photographic emulsion of claim 5 fogged by treatment with thiourea dioxide.

7. The photographic emulsion of claim 1 in which the silver halide grains have a surface of silver bromide.

8. A photographic element comprising a support and at .least one fogged, direct-positive, photographic silver halide emulsion layer having a binding agent comprising a hydrophilic colloid and water-insoluble polymerized vinyl compound in which the binding agent for the emulsion layer comprises about 20 to about 80%, by weight, of polymerized vinyl compound based on the combined weight of hydrophilic colloid and water-insoluble polymerized vinyl compound.

9. The photographic element of claim 8 in which the hydrophilic colloid is gelatin.

-10. The photographic element of claim 8 in which the polymerized vinyl compound is an alkyl acrylate polymer.

11. The photographic element of claim 8 in which the polymeric vinyl compound is a copolymer of an alkyl acrylate with a monomer having the formula:

where R is hydrogen or alkyl, R has its valence bonds on diiferent carbon atoms and is a divalent hydrocarbon radical or a divalent aliphatic hydrocarbon radical in which the chain of carbon atoms joining the oxygen and sulfur atoms of the above formula is interrupted by an oxygen or sulfur atom and M is a cation.

12. The photographic element of claim 8 in which the polymeric vinyl compound is a copolymer of an alkyl 11 acrylate with acrylic acid and a monomer having the formula:

where R, R and R are each hydrogen or alkyl and R and R are each divalent saturated hydrocarbon radicals.

13. The photographic element of claim 8 in which the polymeric vinyl compound is a copolymer of an alkyl acrylate with acrylic acid.

14. The photographic element of claim 8 in which the silver halide grains in the emulsion layer have a surface of silver bromide.

15. The photographic element of claim 8 in which the 12 hydrophilic colloid comprises gelatin and a water soluble vinyl polymer.

16. The photographic element of claim 8 in which the hydrophilic colloid comprises gelatin and water soluble polyacrylamide.

References Cited UNITED STATES PATENTS 3,178,282 7/1965 Luckey et al 96-64 X 3,287,289 11/1966 Ream et al 96-114 X NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant Examiner US. Cl. X.R. 

